The term “steganography” generally means data hiding. One form of data hiding is digital watermarking. Digital watermarking is a process for modifying media content to embed a machine-readable (or machine-detectable) signal or code into the media content. For the purposes of this application, the data may be modified such that the embedded code or signal is imperceptible or nearly imperceptible to a user, yet may be detected through an automated detection process. Most commonly, digital watermarking is applied to media content such as images, audio signals, and video signals.
Digital watermarking systems may include two primary components: an embedding component that embeds a watermark in media content, and a reading component that detects and reads an embedded watermark. The embedding component (or “embedder” or “encoder”) may embed a watermark by altering data samples representing the media content in the spatial, temporal or some other domain (e.g., Fourier, Discrete Cosine or Wavelet transform domains). The reading component (or “reader” or “decoder”) may analyze target content to detect whether a watermark is present. In applications where the watermark encodes information (e.g., a message or payload), the reader may extract this information from a detected watermark.
A watermark embedding process may convert a message, signal or payload into a watermark signal. The embedding process may then combine the watermark signal with media content and possibly another signals (e.g., an orientation pattern or synchronization signal) to create watermarked media content. The process of combining the watermark signal with the media content may be a linear or non-linear function. The watermark signal may be applied by modulating or altering signal samples in a spatial, temporal or some other transform domain.
A watermark encoder may analyze and selectively adjust media content to give it attributes that correspond to the desired message symbol or symbols to be encoded. There are many signal attributes that may encode a message symbol, such as a positive or negative polarity of signal samples or a set of samples, a given parity (odd or even), a given difference value or polarity of the difference between signal samples (e.g., a difference between selected spatial intensity values or transform coefficients), a given distance value between watermarks, a given phase or phase offset between different watermark components, a modulation of the phase of the host signal, a modulation of frequency coefficients of the host signal, a given frequency pattern, a given quantizer (e.g., in Quantization Index Modulation) etc.
The present assignee's work in steganography, data hiding and digital watermarking is reflected, e.g., in U.S. Pat. Nos. 6,947,571; 6,912,295; 6,891,959. 6,763,123; 6,718,046; 6,614,914; 6,590,996; 6,408,082; 6,122,403 and 5,862,260, and in published specifications WO 9953428 and WO 0007356 (corresponding to U.S. Pat. Nos. 6,449,377 and 6,345,104). Each of the above patent documents is hereby incorporated by reference herein in its entirety. Of course, a great many other approaches are familiar to those skilled in the art. The artisan is presumed to be familiar with a full range of literature concerning steganography, data hiding and digital watermarking.
One combination recites a method comprising: obtaining data representing video; using one or more electronic processors, embedding a first watermark signal in a first portion of the data, the first watermark signal comprising a first signal polarity; using one or more electronic processors, embedding a second watermark signal in a second portion of the data, the second watermark signal comprising a second signal polarity that is inversely related to the first signal polarity; rendering the watermarked video in real time, in which due to temporal averaging of the first watermark signal and second watermark signal over time, the first watermark signal and the second watermark signal are hidden from a human observer of the video.
Another combination includes a method comprising: obtaining data representing video; using one or more electronic processors, embedding a watermark signal in a first portion of the data, the embedding using a first embedding bump size; using one or more electronic processors, embedding a watermark signal in a second portion of the data, the embedding using a second embedding bump size, in which the first embedding bump size corresponds with a first optimal detection range distance when capturing optical scan data associated with the video as it is being rendered on a display, and the second embedding bump size corresponds with a second, larger optimal detection range distance when capturing optical scan data associated with the video as it is being rendered on the display.
Yet another combination includes a method comprising: obtaining a watermark signal; using one or more programmed electronic processors, embedding a watermark signal in a first portion of a video signal; preconditioning the watermark signal in a first manner to allow expanded detection of said preconditioned watermark signal in the face of first distortion; using one or more programmed electronic processors, embedding the watermark signal preconditioned in the first manner in a second portion of the video signal; preconditioning the watermark signal in a second manner to allow expanded detection of said preconditioned watermark signal in the face of second distortion; using one or more programmed electronic processors, embedding the watermark signal preconditioned in the second manner in a third portion of the video signal.
Still another combination recites a method comprising: receiving data representing video captured from a video display; searching the data for hidden indicia, the indicia providing information to allow a determination of video capture distance and video capture perspective; upon encountering the hidden indicia, using the information to warp the data to compensate for distortion caused by video capture distance or video capture perspective; provided the warped data to an electronic processor programmed as a steganographic indicia decoder, said decoder analyzes the warped data to decode steganographic indicia hidden in video captured from the video display.
On aspect of the disclosure is to facilitate watermark detection from video captured of a monitor or display (e.g., TV, computer monitor, smartphone display, etc.). Watermark detection over wider viewing angles can be obtained by pre-distorting a watermark signal to introduce perspective distortion. For example, let's say the watermark is pre-distorted such that it has a perspective corresponding to a +30 degree horizontal or vertical tilt. With a +30 degree pre-distortion, an image capture at −30 degree horizontal or vertical tilt appears head-on (e.g., no perspective in the video capture), allowing detection to proceed as normal.
Further combinations, aspects, features and advantages will become even more apparent with reference to the following detailed description and accompanying drawing.